How do I receive entities from a simulator in mosaik?

[Ma1t3]

How can I have the entities of a ModelFactory returned from the ModelFactory or the entity dictionary (containing eid, full_id, sid, sim_name and type) returned after calling create()?

I got a snippet of csv reader to provide an example:

load_sim = world.start("CSVSim", scenario_config=scenario_config)
loads_csv = load_sim.household_csv.create(1,init_vals)

In this example, entities can be retrieved via load_sim._sim.proxy.sim.entities, but this accesses the private attribute _sim, which is not best practice.
Additionally, there is also the possibility to do this via world.sims[loads_csv[0].sid].proxy.sim.entities, but I also see this as a workaround rather than a sensible solution.
I looked a bit in the documentation but didn't find anything suitable. Can you help me out?

[Ma1t3]

In principle, there is actually no designated method for accessing the simulator-internal entities in the scenario script. How they are stored exactly can vary from simulator to simulator. Plus, if the simulator is not written in Python and does not run in the same process as mosaik, there is no way to do this.
So the world.sims[...].proxy.sim method you proposed is about as hacky as it feels.

The "right" solution would be to extend the simulator whose internal entities you would like to have with a corresponding extra_method that returns these entities or the information required from them. More information about extra_methods and how to use them can be found here: simulator-docs
Unfortunately, with external simulators these methods can no longer be called after the simulation has run.